Restart iPhone. Hold down the Sleep/Wake button until the red slider appears. Slide your finger across the slider to turn off iPhone. To turn iPhone back on, hold down the Sleep/Wake button until the Apple logo appears.

Force an app to quit. From the Home screen, double-click the Home button and swipe upwards on the app screen.

If you can't turn off iPhone or if the problem continues, you may need to reset iPhone. Do this only if you're unable to restart your iPhone.

Reset iPhone. Hold down the Sleep/Wake button and the Home button at the same time for at least ten seconds, until the Apple logo appears.

You can reset the word dictionary, network settings, home screen layout, and location warnings. You can also erase all of your content and settings.